Sonoluminescence is a well-known phenomena discovered in the 1930's in which light is generated when a liquid is cavitated. Although a variety of techniques for cavitating the liquid are known (e.g., spark discharge, laser pulse, flowing the liquid through a Venturi tube), one of the most common techniques is through the application of high intensity sound waves.
In essence, the cavitation process consists of three stages; bubble formation, growth and subsequent collapse. The bubble or bubbles cavitated during this process absorb the applied energy, for example sound energy, and then release the energy in the form of light emission during an extremely brief period of time. The intensity of the generated light depends on a variety of factors including the physical properties of the liquid (e.g., density, surface tension, vapor pressure, chemical structure, temperature, hydrostatic pressure, etc.) and the applied energy (e.g., sound wave amplitude, sound wave frequency, etc.).
Although it is generally recognized that during the collapse of a cavitating bubble extremely high temperature plasmas are developed, leading to the observed sonoluminescence effect, many aspects of the phenomena have not yet been characterized. As such, the phenomena is at the heart of a considerable amount of research as scientists attempt to not only completely characterize the phenomena (e.g., effects of pressure on the cavitating medium), but also its many applications (e.g., sonochemistry, chemical detoxification, ultrasonic cleaning, etc.).
In order to study the sonoluminescence phenomena, it is clearly important to be able to closely monitor the cavitating bubbles as well as the intensity, frequency and timing of the resultant sonoluminescence. Additionally, some research may require probing the cavitating liquid. Lastly, many cavitation experiments utilize external means of introducing the bubbles into the liquid, for example bubble tubes or hot wires, thus requiring further means of entering the cavitating medium.
Although access to the liquid within a cavitation chamber is typically required before, during and after a cavitation experiment, typically this does not present a problem as most cavitation research is performed at relatively low pressure. As such, glass or other transparent material is generally used for the chamber, thus providing an easy means of monitoring on-going experiments. Additionally, such experiments often use standard beakers or flasks as the cavitation chamber, allowing convenient access to the cavitation medium.
U.S. Pat. No. 4,333,796 discloses a cavitation chamber that is generally cylindrical although the inventors note that other shapes, such as spherical, can also be used. As disclosed, the chamber is comprised of a refractory metal such as tungsten, titanium, molybdenum, rhenium or some alloy thereof and the cavitation medium is a liquid metal such as lithium or an alloy thereof. Surrounding the cavitation chamber is a housing which is purportedly used as a neutron and tritium shield. Projecting through both the outer housing and the cavitation chamber walls are a number of acoustic horns. The specification only discloses that the horns, through the use of flanges, are secured to the chamber/housing walls in such a way as to provide a seal. Similarly, although the specification discloses the use of a tube to distribute H-isotopes into the host material during cavitation, the specification does not disclose how the tube is to be sealed as it passes through the chamber/housing walls. Similarly U.S. Pat. No. 4,563,341, a continuation-in-part of U.S. Pat. No. 4,333,796, does not disclose means for the inclusion of a port with the disclosed cylindrical chamber.
U.S. Pat. No. 5,659,173 discloses a sonoluminescence system that uses a transparent spherical flask. The spherical flask is not described in detail, although the specification discloses that flasks of Pyrex®, Kontes®, and glass were used with sizes ranging from 10 milliliters to 5 liters. As the disclosed flask is transparent, the PMT used to monitor the sonoluminescence was external to the chamber. The drivers as well as a microphone piezoelectric were epoxied to the exterior surface of the chamber. The use of a transparent chamber also allowed the use of an external light source, e.g., a laser, to determine bubble radius without requiring the inclusion of a window in the chamber walls.
U.S. Pat. No. 5,858,104 discloses a shock wave chamber partially filled with a liquid. The remaining portion of the chamber is filled with gas which can be pressurized by a connected pressure source. Acoustic transducers are used to position an object within the chamber. Another transducer delivers a compressional acoustic shock wave into the liquid. A flexible membrane separating the liquid from the gas reflects the compressional shock wave as a dilation wave focused on the location of the object about which a bubble is formed. The patent simply discloses that the transducers are mounted in the chamber walls without stating how the transducers are to be mounted. Similarly, there is no discussion of mounting ports (e.g., view ports) within the chamber walls.
U.S. Pat. No. 6,361,747 discloses an acoustic cavitation reactor in which the reactor chamber is comprised of a flexible tube. The liquid to be treated circulates through the tube. Electroacoustic transducers are radially distributed around the tube, apparently coupled to the flexible tube by being pressed against the exterior surface of the tube. The heads of the transducers have the same curvature as the tube, thus helping to couple the acoustic energy. A film of lubricant interposed between the transducer heads and the wall of the tube further aid the coupling of the acoustic energy to the tube.
Although not in the field of sonoluminescence, U.S. Pat. No. 4,448,743 discloses a confinement chamber for use with an ultra-high temperature steady-state plasma. The specification refers to the plasma as a plasmasphere but is unclear as to whether the confinement chamber is spherical or cylindrical in nature. The disclosed chamber includes multiple transparent ports, for example made of germanium or sodium chloride, but does not disclose how the ports are fabricated or installed within the chamber.
One approach to fabricating a high pressure spherical cavitation chamber is disclosed in co-pending patent application Ser. No. 10/925,070, filed Aug. 23, 2004, entitled Method of Fabricating a Spherical Cavitation Chamber. In order to provide optimum high pressure performance, in addition to being spherically shaped, the inside spherical surface has only a very minor fabrication seam. Such a chamber, however, provides a challenge as to port mounting, especially if the smooth inside surface and the high pressure aspects of the chamber are to be maintained.
Accordingly, what is needed is a means of including one or more ports in a high pressure cavitation chamber. The present invention provides such a port assembly.